Multi-layer filter fabric

Abstract

A multi-layer filter fabric includes a first layer that includes a first non-woven fabric and a second layer that includes a second non-woven fabric. Each layer may include multiple webs. The first and second layers have different median pores sizes and porosities, with the first layer having a larger median pore size and/or porosity than the second layer. The first and second layers may be separated by a scrim. The first and second layers are colored or have visible markings such that the first and second layers are readily distinguished from each other. The multi-layer filter fabric is arranged so that a fluid may enter the multi-layer filter fabric through the first layer and exit through the second layer.

We claim: 
     
         1 . A multi-layer filter fabric, comprising a first layer including a first non-woven fabric and a second layer including a second non-woven fabric, said first layer having a first plurality of pores, said second layer having a second plurality of pores, said first plurality of pores having a first median pore size, said second plurality of pores having a second median pore size, wherein said first median pore size is greater than said second median pore size. 
     
     
         2 . The multi-layer filter fabric of  claim 1 , wherein said first layer has a first porosity, said second layer has a second porosity, and said first porosity is greater than said second porosity. 
     
     
         3 . The multi-layer fabric of  claim 1 , wherein said first layer includes a plurality of first webs, and at least one of said first webs includes said first non-woven fabric. 
     
     
         4 . The multi-layer fabric of  claim 1 , wherein said second layer includes a plurality of second webs, and at least one of said second webs includes said second non-woven fabric. 
     
     
         5 . The multi-layer filter fabric of  claim 1 , wherein said multi-layer filter fabric is arranged so that a fluid enters said multi-layer filter fabric through said first layer, and exits said multi-layer filter fabric through said second layer. 
     
     
         6 . The multi-layer filter fabric of  claim 5 , wherein said first layer has one or both of a first color and/or a first marking, and said second layer has one or both of a second color and a second marking such that said second layer is visibly distinguished from said first layer. 
     
     
         7 . The multi-layer filter fabric of  claim 6 , wherein said first layer includes a plurality of first fibers having said first color. 
     
     
         8 . The multi-layer filter fabric of  claim 6 , wherein said second layer includes a plurality of second fibers having said second color. 
     
     
         9 . The multi-layer filter fabric of  claim 1 , further including a scrim between said first layer and said second layer. 
     
     
         10 . The multi-layer filter fabric of  claim 1 , wherein said first non-woven fabric and/or said second non-woven fabric includes fibers selected from the group consisting of polyethylene fibers, polypropylene fibers, polyester fibers, synthetic fibers, bicomponent fibers, and blends thereof. 
     
     
         11 . The multi-layer filter fabric of  claim 1 , wherein said first non-woven fabric and/or said second non-woven fabric includes fibers having weights in the range of 0.4 denier to 100 denier. 
     
     
         12 . The multi-layer filter fabric of  claim 1 , wherein said first non-woven fabric and/or said second non-woven fabric includes a blend of fibers having different weights in the range of 0.4 denier to 100 denier. 
     
     
         13 . The multi-layer filter fabric of  claim 1 , wherein the multi-layer filter fabric has a weight in the range of 0.5 ounces-per-square-yard to 36 ounces-per-square yard. 
     
     
         14 . The multi-layer filter fabric of  claim 1 , wherein the multi-layer filter fabric has a thickness in the range of 0.005 inch to 3.8 inches. 
     
     
         15 . The multi-layer filter fabric of  claim 1 , wherein the multi-layer filter fabric consists of said first layer and said second layer, and optionally a scrim, and has an MERV rating of 8 or greater. 
     
     
         16 . The multi-layer filter fabric of  claim 1 , further comprising a finish on said multi-layer filter fabric. 
     
     
         17 . The multi-layer filter fabric of  claim 1 , further comprising microparticles and/or nanoparticles of a material selected from the group consisting of a synthetic polymer, carbon, minerals, resins, and mixtures thereof. 
     
     
         18 . The multi-layer filter fabric of  claim 17 , wherein said microparticles and/or said nanoparticles are within said first non-woven fabric and/or said second non-woven fabric. 
     
     
         19 . The multi-layer filter fabric of  claim 1 , wherein said multi-layer filter fabric includes an additive selected from the group consisting of thermoplastic materials, resins, fillers, antimicrobials, antifungals, coloring agents, and other additives known for use in textiles. 
     
     
         20 . The multi-layer filter fabric of  claim 19 , wherein said additive is within said first non-woven fabric and/or said second non-woven fabric.